diff options
| author | Oleksij Rempel <o.rempel@pengutronix.de> | 2025-07-03 13:49:41 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-07-17 18:37:06 +0200 |
| commit | 4d5476fa3931230c36b568b4c85dd3b8b0a387cc (patch) | |
| tree | 9a69d02fc021c25c2be0c0c97a4ed4bda60bb6f1 | |
| parent | 6fb4cd247cda78e821768d7b18e55c9941633a2e (diff) | |
net: phy: smsc: Fix link failure in forced mode with Auto-MDIX
[ Upstream commit 9dfe110cc0f6ef42af8e81ce52aef34a647d0b8a ]
Force a fixed MDI-X mode when auto-negotiation is disabled to prevent
link instability.
When forcing the link speed and duplex on a LAN9500 PHY (e.g., with
`ethtool -s eth0 autoneg off ...`) while leaving MDI-X control in auto
mode, the PHY fails to establish a stable link. This occurs because the
PHY's Auto-MDIX algorithm is not designed to operate when
auto-negotiation is disabled. In this state, the PHY continuously
toggles the TX/RX signal pairs, which prevents the link partner from
synchronizing.
This patch resolves the issue by detecting when auto-negotiation is
disabled. If the MDI-X control mode is set to 'auto', the driver now
forces a specific, stable mode (ETH_TP_MDI) to prevent the pair
toggling. This choice of a fixed MDI mode mirrors the behavior the
hardware would exhibit if the AUTOMDIX_EN strap were configured for a
fixed MDI connection.
Fixes: 05b35e7eb9a1 ("smsc95xx: add phylib support")
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Cc: Andre Edich <andre.edich@microchip.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20250703114941.3243890-4-o.rempel@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | drivers/net/phy/smsc.c | 25 |
1 files changed, 22 insertions, 3 deletions
diff --git a/drivers/net/phy/smsc.c b/drivers/net/phy/smsc.c index 09fbc30bfd3d..6a43f6d6e85c 100644 --- a/drivers/net/phy/smsc.c +++ b/drivers/net/phy/smsc.c @@ -155,10 +155,29 @@ static int smsc_phy_reset(struct phy_device *phydev) static int lan87xx_config_aneg(struct phy_device *phydev) { - int rc; + u8 mdix_ctrl; int val; + int rc; + + /* When auto-negotiation is disabled (forced mode), the PHY's + * Auto-MDIX will continue toggling the TX/RX pairs. + * + * To establish a stable link, we must select a fixed MDI mode. + * If the user has not specified a fixed MDI mode (i.e., mdix_ctrl is + * 'auto'), we default to ETH_TP_MDI. This choice of a ETH_TP_MDI mode + * mirrors the behavior the hardware would exhibit if the AUTOMDIX_EN + * strap were configured for a fixed MDI connection. + */ + if (phydev->autoneg == AUTONEG_DISABLE) { + if (phydev->mdix_ctrl == ETH_TP_MDI_AUTO) + mdix_ctrl = ETH_TP_MDI; + else + mdix_ctrl = phydev->mdix_ctrl; + } else { + mdix_ctrl = phydev->mdix_ctrl; + } - switch (phydev->mdix_ctrl) { + switch (mdix_ctrl) { case ETH_TP_MDI: val = SPECIAL_CTRL_STS_OVRRD_AMDIX_; break; @@ -184,7 +203,7 @@ static int lan87xx_config_aneg(struct phy_device *phydev) rc |= val; phy_write(phydev, SPECIAL_CTRL_STS, rc); - phydev->mdix = phydev->mdix_ctrl; + phydev->mdix = mdix_ctrl; return genphy_config_aneg(phydev); } |